High-frequency (HF) surgery, of which plasma coagulation is a subset, has been used for many years, both in human medicine and in veterinary medicine, to coagulate and/or cut biological tissue. Suitable electrosurgical instruments are used to pass high-frequency current through the tissue to be treated, so that this tissue changes as a result of protein coagulation and dehydration. Vessels can be sealed and bleeding stopped through this coagulation process. A cutting process that follows the coagulation process enables full separation of tissue that has already coagulated.
Plasma coagulation enables a non-contact coagulation of tissue and serves for effective haemostasis and devitalization of tissue. In this type of coagulation, inert working gas, for example argon, is passed via gas supply devices from a plasma coagulation instrument to the tissue to be treated. With the help of the working gas, a “plasma jet” can be generated between an electrode at a distal end of the gas supply device, such as a probe, and the tissue. The HF current can then be applied to the tissue to be treated without the electrosurgical instrument coming into contact with the tissue. This therefore avoids adherence of the tissue to the instrument.
Furthermore, with resection of tissue, in particular tumor tissue in the gastrointestinal tract, which is limited to the mucosa, it should be ectomized in a single session and as completely as possible. To enable tumors that have a large surface area with a diameter of more than eight centimeters to be ectomized in one session and as completely as possible, it is proposed in WO 2006/108480 A1, for example, that for endoscopic mucosal resection, prior to resection, the mucosa is first injected with liquid using a flexible needle. The needle is thereby placed in the submucosa. The penetration of the liquid into the mucosa causes it to separate from the muscularis propria, with a fluid cushion forming beneath the mucosa: This creates a safety distance from the muscularis propria, and confers thermal protection. Mucosal resection is then carried out, for example, with a flexible needle knife, but in particular with the above-described HF surgical instrument.
With a water jet surgical instrument according to the prior art, a bundled water jet is discharged at a distal end of the instrument at high pressure which penetrates the soft mucosa. The penetrating liquid is collected in the submucosa (in the resilient fibrous displacement layer) such that a fluid cushion forms.
The above-described treatments can also result in internal bleeding, which obstructs the view of the surgeon, so that the operating site has to be rinsed. A suitable rinsing probe is generally provided for this purpose.
A disadvantage of the above-described procedures is that a separate instrument is required for each one, necessitating a time-consuming change of the respective instrument for each new intervention. Furthermore, plasma coagulation that is gentle to tissue is only possible at low power and/or with short application times, since at higher power levels carbonization of coagulated tissue cannot be reliably ruled out. The carbonization can lead to inflammation of the tissue and an increase in post-operative problems. The generation of smoke and plume, which is accompanied by an unpleasant odor, is also not ruled out with certainty with carbonization. Moreover, the smoke obscures the vision of the surgeon and for this reason must be avoided. Another disadvantage is the development of concentrated current paths during plasma coagulation, resulting in inhomogeneous damage to tissue. Lastly, oozing bleeding that can occur during the intervention is difficult to localize using the known instruments.